1. Chapter 12: DNA and RNA

2. KWL Chart What I KNOW already about DNA What I WANT to know about DNA
What I have LEARNED about DNA

3. Learning Targets for Section 12-1
Summarize the relationship between genes and DNA?
Describe the overall structure of DNA?

4. 12–1 Research Behind DNA Griffith and Transformation
In 1928, British scientist Frederick Griffith tried to determine which bacteria produced pneumonia.
Griffith isolated two different strains.
1. disease-causing = smooth colonies
2. harmless strain = rough colonies.

5. Griffith's Experiment Griffith injected mice
1. disease-causing bacteria- mice developed pneumonia and died.
2. harmless strain - didn’t get sick at all

6. Experiment cont.
Griffith’s then mixed heat-killed, disease-causing bacteria with live, harmless ones and injected the mixture into mice
Mice developed pneumonia and many died.
Found their lungs filled with the disease-causing bacteria

7. Figure 12–2 Griffith’s Experiment
Section 12-1
Heat-killed, disease-causing bacteria (smooth colonies)
Harmless bacteria (rough colonies)
Control (no growth)
Harmless bacteria (rough colonies)
Heat-killed, disease-causing bacteria (smooth colonies)
Disease-causing bacteria (smooth colonies)
Dies of pneumonia
Dies of pneumonia
Lives
Lives
Live, disease-causing bacteria (smooth colonies)
Go to Section:

8. Figure 12–2 Griffith’s Experiment
Section 12-1
Heat-killed, disease-causing bacteria (smooth colonies)
Harmless bacteria (rough colonies)
Control (no growth)
Harmless bacteria (rough colonies)
Heat-killed, disease-causing bacteria (smooth colonies)
Disease-causing bacteria (smooth colonies)
Dies of pneumonia
Dies of pneumonia
Lives
Lives
Live, disease-causing bacteria (smooth colonies)
Go to Section:

9. Figure 12–2 Griffith’s Experiment
Section 12-1
Heat-killed, disease-causing bacteria (smooth colonies)
Harmless bacteria (rough colonies)
Control (no growth)
Harmless bacteria (rough colonies)
Heat-killed, disease-causing bacteria (smooth colonies)
Disease-causing bacteria (smooth colonies)
Dies of pneumonia
Dies of pneumonia
Lives
Lives
Live, disease-causing bacteria (smooth colonies)
Go to Section:

10. Griffith’s Conclusion:
Griffith hypothesized some factor transformed harmless cells into the heat-killed harmful cells
Griffith movie

11. Avery and DNA
Avery and his colleagues repeated Griffith’s experiment then:
Used enzymes that destroyed proteins, lipids, carbohydrates, and other molecules, including the nucleic acid RNA
When they destroyed the nucleic acid (DNA), transformation did not occur

12. Avery’s Conclusion:
Avery and other scientists discovered that DNA is the nucleic acid that stores and transmits the genetic information from one generation of an organism to the next

13. The Hershey Chase Experiment
Martha Chase and Alfred Hershey

14. The Hershey Chase Experiment
Studied viruses, nonliving particles smaller than a cell that can infect living organisms
Hershey and Chase reasoned that if they could determine which part of the virus—the protein coat or the DNA core—entered the infected cell, they would learn whether genes were made of protein or DNA
They grew viruses in cultures of radioactive isotopes of phosphorus-32 (32P) and sulfur-35 (35S).

15. The Hershey Chase Experiment
Proteins contain almost no phosphorus and DNA contains no sulfur
If 35S was found in the bacteria, it would mean that the viruses’ protein had been injected, If 32P was found in the bacteria, then it was the DNA that had been injected

16. Figure 12–4 Hershey-Chase Experiment
Section 12-1
Bacteriophage with phosphorus-32 in DNA
Phage infects bacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infects bacterium
No radioactivity inside bacterium
Go to Section:

17. Figure 12–4 Hershey-Chase Experiment
Section 12-1
Bacteriophage with phosphorus-32 in DNA
Phage infects bacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infects bacterium
No radioactivity inside bacterium
Go to Section:

18. Figure 12–4 Hershey-Chase Experiment
Section 12-1
Bacteriophage with phosphorus-32 in DNA
Phage infects bacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infects bacterium
No radioactivity inside bacterium
Go to Section:

19. Hershey and Chase’s Conclusion:
Hershey and Chase concluded that the genetic material of the bacteriophage was DNA, not protein.

21. REVIEW In your science journal:
List as many scientists you can remember
And describe their contribution to our understanding of DNA

22. The Structure of DNA
DNA is a long molecule made up of units called nucleotides
Each nucleotide is made up of three parts:
1. a 5-carbon sugar called deoxyribose,
2. a phosphate group,
3. and a nitrogenous (nitrogen- containing) base

23. There are four kinds of nitrogenous bases in DNA
Purines:
Adenine: Expressed A
Guanine: Expressed G
Pyrimidines:
Thymine: Expressed T
Cytocine: Expressed C

24. Figure 12–5 DNA Nucleotides
Section 12-1
Purines
Pyrimidines
Adenine
Guanine
Cytosine
Thymine
Phosphate group
Deoxyribose
Go to Section:

25. Chargaff’s Rules
Erwin Chargaff, an American biochemist, discovered that the percentages of guanine [G] and cytosine [C] are almost equal in any sample of DNA
The same thing is true for adenine [A] and thymine [T]
Despite the fact that DNA samples from organisms obeyed this rule, neither Chargaff nor anyone else had the faintest idea why

27. X-Ray Evidence
In the early 1950s, a British scientist named Rosalind Franklin began to study DNA using a technique called X-ray diffraction
The X-shaped pattern in the image shows that the strands in DNA are twisted around each other like the coils of a spring, a shape known as a helix

29. The Double Helix 
At the same time Francis Crick, and James Watson, were trying to understand the structure of DNA by building three-dimensional models of the molecule
In 1953, Watson was shown a copy of Franklin’s X-ray pattern. In his book The Double Helix, Watson wrote: “The instant I saw the picture my mouth fell open and my pulse began to race.”

32. Watson and Crick’s Conclusion:
- DNA is a double helix in which two strands are wound around each other.
- Each strand is made up of a chain of nucleotides.
- The two strands are held together by hydrogen bonds between adenine and thymine and between guanine and cytosine.

33. Structure of DNA

34. Learning Targets for Section 12.2
Summarize the events that happen in DNA replication
Relate the DNA molecule to chromosome structure.

35. 12–2 Chromosomes and DNA Replication
DNA and Chromosomes
Most prokaryotes have a single circular DNA molecule that contains nearly all of the cell’s genetic information

36. Prokaryotic Chromosome Structure
Section 12-2
Chromosome
E. coli bacterium
Bases on the chromosome
Go to Section:

37. Differences between Prokaryotes and Eukaryotes
Eukaryotic DNA is a bit more complicated. Many eukaryotes have as much as 1000 times the amount of DNA as prokaryotes
DNA Length DNA molecules are surprisingly long
The chromosome of the prokaryote E. coli, contains 4,639,221 base pairs

39. Length of DNA
This means that the nucleus of a human cell contains more than 1 meter of DNA
How can so much DNA be packed into each and every cell in our body?

40.   Chromosome Structure
Eukaryotic chromosomes contain both DNA and protein, tightly packed together to form a substance called chromatin
Chromatin consists of DNA that is tightly coiled around proteins called histones

41.   Chromosome Structure
Together, the DNA and histone molecules form a beadlike structure called a nucleosome
This allows the chromosomes to be very tightly coiled up in the nucleus

42. Figure 12-10 Chromosome Structure of Eukaryotes
Section 12-2
Chromosome
Nucleosome
DNA
double
helix
Coils
Supercoils
Histones
Go to Section:

43. DNA Structure Activity

44. DNA Replication
When Watson and Crick discovered the double helix structure of DNA, there was one more remarkable aspect that they recognized immediately.
The structure explained how DNA could be copied, or replicated
Each strand of the DNA double helix has all the information needed to reconstruct the other half by the mechanism of base pairing

46. DNA Replication 
During DNA replication, the DNA molecule separates into two strands
Then produces two new complementary strands following the rules of base pairing.
Each strand of the double helix of DNA serves as a template, or model, for the new strand

47. Figure 12–11 DNA Replication
Section 12-2
Original strand
New strand
DNA polymerase
Growth
DNA polymerase
Growth
Replication fork
Replication fork
Nitrogenous bases
New strand
Original strand
Go to Section:

48. DNA Replication 
DNA replication animation
DNA Replication animation

49. How DNA Replicates Start with a double strand of DNA
DNA replication is carried out by a series of enzymes. which “unzip” a molecule of DNA

50. How DNA Replicates A – T G – C C – G T – A
I’ve deleted the sugar-phosphate backbone for easier drawings
Hydrogen bonds

51. DNA Unzips A – T A - T G – C G - C A – T A T C – G DNA C G
T – A unzips T A
C – G C G

52. A – T G – C DNA PolymeraseIII A T C G T A C G
DNAP III moves along each strand adding a base pair at a time

53. A – T
G – C
A T T
C G G
T T A
C CG
DNAP III continues to moves along each strand adding a base pair at a time

54. "Replication Fork"
A – T
G – C
A T A T
C G C G
T A TA
C G CG

55. Finally get 2 new strands, exact copies
AT AT
GC GC
CG CG
TA TA

56. STOP: Practice Replicate the following strand of DNA
ATG GGA CCG TAT ACG GAG
TAC CCT GGC ATA TGC CTC

57. DNA and Enzymes
DNA replication involves a host of enzymes and regulatory molecules
The principal enzyme involved in DNA replication is called DNA polymerase
In addition to replication DNA polymerase also “proofreads” each new DNA strand, helping to maximize the odds that each molecule is a perfect copy of the original DNA

58. Learning Targets for Section 12.3
What are the three main types of RNA?
What is transcription?
What is translation?

59. 12–3 RNA and Protein Synthesis
The double helix structure explains how DNA can be replicated but it does not explain how a gene works
Genes are coded DNA instructions that control the production of proteins

61. RNA
The first step is to copy part of the nucleotide sequence from DNA into RNA a process called transcription
RNA molecules then carry out the process of making proteins.
RNA molecule is a working copy of a single gene.
Using RNA makes it possible for a single gene to produce hundreds or even thousands of RNA molecules

62. The Structure of RNA
There are three main differences between RNA and DNA:
The sugar in RNA is ribose instead of deoxyribose
RNA is generally single-stranded
RNA contains uracil in place of thymine

63. Types of RNA
There are three main types of RNA: messenger RNA, ribosomal RNA, and transfer RNA.
messenger RNA (mRNA) serves as “messengers” from DNA to the rest of the cell.
ribosomal RNA (rRNA) is the site where Proteins are assembled on ribosomes
transfer RNA (tRNA) transfers each amino acid to the ribosome during the construction of a protein.

64. Transcription
During transcription, RNA polymerase binds to DNA and separates the DNA strands.
RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA

65. Figure 12–14 Transcription
Section 12-3
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
RNA polymerase
DNA
RNA
Go to Section:

66. Transcription
Transcription movie

67. Practice Transcribing
Remember A goes with T, C goes with G and Uracil takes the place of Thymine
TAC GCA CCA TAT CCG ATT
AUG CGU GGU AUA GGC UAA

68. Where to Begin?
The enzyme will bind only to regions of DNA known as promoters, which have specific base sequences.
Promoters are signals in DNA that indicate to the enzyme where to bind to make RNA
Similar signals in DNA cause transcription to stop when the new RNA molecule is completed

69. Editing RNA
Many RNA molecules have sections, called introns, edited out of them before they become functional.
The remaining pieces, called exons, are spliced together.
Then, a cap and tail are added to form the final RNA molecule.

71. The Genetic Code
The “language” of mRNA instructions is called the genetic code.
RNA contains four different bases: A, U, C, and G.
In effect, the code is written in a language that has only four “letters.”

72. STOP THINK! What is the process of transcription making?
Where does transcription take place?
What enzymes are used to complete transcription?
Compare and Contrast DNA and RNA?

73. Genetic Code The genetic code is read three letters at a time
Each three-letter “word” in mRNA is known as a codon
A codon consists of three consecutive nucleotides that specify a single amino acid that is to be added to the polypeptide

74. Genetic Code
Because there are four different bases, there are 64 possible three-base codons (4 × 4 × 4 = 64).
The codon, AUG, that can either specify methionine or serve as the initiation, or “start,” codon for protein synthesis
There are three “stop” codons that do not code for any amino acid

76. Translation
During translation, the cell uses information from messenger RNA to produce proteins
This process is known as translation

77. Translation
Before translation can occur, messenger RNA must first be transcribed from DNA in the nucleus and released into the cytoplasm
Translation begins when an mRNA molecule in the cytoplasm attaches to a ribosome

78. Figure 12–18 Translation Section 12-3 mRNA Go to Section: Nucleus
Messenger RNA
Messenger RNA is transcribed in the nucleus.
mRNA
Lysine
Phenylalanine
tRNA
Transfer RNA
The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon.
Methionine
Ribosome
mRNA
Start codon
Go to Section:

79. Translation
As each codon of the mRNA molecule moves through the ribosome, the proper amino acid is brought into the ribosome and attached to the growing polypeptide chain
That job is done by transfer RNA

80. Translation
The codon matches up with complementary bases on the tRNA to tell it which amino acid to bring in
The three bases on the tRNA molecule, called the anticodon, are complementary to one of the mRNA codons

81. Translation
The polypeptide chain continues to grow until the ribosome reaches a stop codon on the mRNA molecule
At that point the protein is released to be modified in the Golgi apparatus or to be shipped out to perform its function

82. Figure 12–18 Translation (continued)
Section 12-3
The Polypeptide “Assembly Line”
The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids.
Growing polypeptide chain
Ribosome
tRNA
Lysine
tRNA
mRNA
Completing the Polypeptide
The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain.
mRNA
Translation direction
Ribosome
Go to Section:

83. Practice Translating original DNA ATG CCC AGT TCA TAA
Compl DNA = ___ ___ ____ ___ ____
mRNA = ____ ___ ____ ____ ____
Amino acid ______________, _______________, _____________, ______________, _____________.

84. Check these answers first
original DNA ATG CCC AGT TCA TAA
Compl DNA = TAC GGG TCA AGT ATT
mRNA = AUG CCC AGU UCA UAA

86. Amino Acid Answers Amino acid methionine, proline,
serine, serine, stop

88. BELLRINGER 11/11/09 COMPARE/CONTRAST RNA TO DNA
*** Include as much information about each that you can think of
THEN DESCRIBE what happens during TRANSCRIPTION
And DESCRIBE WHAT HAPPENS DURING TRANSLATION

89. 12.4 Learning Targets
Describe how gene mutations and chromosomal mutations occur
Understand the difference between point mutations and frameshift mutations

90. Ways variations can arise
What is a mutation and where can it occur? Inheritable change in genetic code
* 99.9 % are harmful. Only 0.1% are helpful!!
What is a chromosomal mutation?
Changes in number or structure of chromosome
When do chromosomal mutations occur?
During Meiosis – A cell division that produces gametes

91. TYPES OF MUTATIONS What is a frameshift mutation?
Change that shifts the genetic message through inserting or deleting a nucleotide
What is a point mutation?
Change at one point of a chromosome.

92. What is a deletion mutation?
Loss of one or more genes
What is a duplication mutation?
One or more genes are copied twice
What is an inversion mutation?
Part of a chromosome gets turned the wrong way